Nickel and cobalt plated sponge catalysts

ABSTRACT

Novel nickel and/or cobalt plated sponge based catalysts are disclosed. The catalyst have an activity and/or selectivity comparable to conventional nickel and/or cobalt sponge catalysts, e.g., Raney® nickel or Raney® cobalt catalysts, but require a reduced content of nickel and/or cobalt. Catalysts in accordance with the invention comprise nickel and/or cobalt coated on at least a portion of the surface of a sponge support. Preferably, the sponge support comprises at least one metal other than or different from the metal(s) contained in the coating. The method of preparing the plated catalysts, and the method of using the catalysts in the preparation of organic compounds are also disclosed.

FIELD OF THE INVENTION

The present invention relates to novel sponge catalysts and to processesfor the preparation and use thereof. More specifically, the presentinvention relates to novel nickel and/or cobalt plated sponge catalysts,the method of preparing the catalysts, and the method of using thecatalysts in the preparation of organic compounds.

BACKGROUND OF THE INVENTION

Catalysts based on highly porous nickel materials are well known. Suchmaterials are part of a family of metal alloy derived products sold byW. R. Grace & Co. Conn. under the trademark “Raney®.” These porousmaterials, when microscopically viewed, take on a sponge-like appearancehaving tortuous pore channels throughout the nickel particle. Thus, suchmetal alloy materials are generically viewed as sponge products. Thesponge catalyst product is normally referred to in terms of the metalwhich constitutes the major component of the sponge product. These highsurface area products have been found to have sites for hydrogenactivation and, thus, exhibit catalytic activity when used in thepreparation of various organic compounds, such as, for example, thehydrogenation of nitro-substituted organics to their corresponding aminecompound.

In general, sponge catalysts, such as porous nickel catalysts are formedby first producing a base metal-aluminum (preferred) or basemetal-silicon alloy using conventional metallurgical techniques. Theformed alloy is ground into a fine powder and classified by passing itthrough a sieve to provide a material having a desired particle size,which is normally less than 500 microns and, preferably less than 75microns. Larger particles are recycled for further grinding.

The alloy powder is then treated with a solution of a base to leach outa substantial amount of the aluminum metal or silicon present. The basemay be selected from either an inorganic (preferred) or organiccompound. For example, in conventional processes an aqueous solutionhaving from about 5 to 50 weight percent concentration of an alkalimetal hydroxide (e.g., sodium hydroxide) is employed as the leachingagent. The treatment of the alloy is usually carried out at elevatedtemperatures of from about 40° C. to 110° C. The alloy powder can bedirectly added to the alkali solution or it can be formed into anaqueous suspension, which is then contacted with the alkali solution.The aluminum contained in the alloy dissolves to form an alkali metalaluminate (e.g., sodium aluminate) with vigorous evolution of hydrogen.When silicon is in the alloy, the base forms the corresponding alkalimetal silicate. The powder and alkali are normally allowed to remain incontact with each other for several hours at elevated temperature (e.g.,40°-110° C.) until the aluminum (or silicon) content is reduced to thedesired level. The crude sponge catalyst is separated from the reactionliquor and then conventionally washed with water until the wash waterhas a slightly alkaline pH value of about 8. The pore volume, pore sizeand surface area of the leached alloy will depend upon the amount ofaluminum (or silicon) in the initial alloy and the degree of leaching.

The metal alloy used to prepare sponge catalysts is generally composedof a major amount of a base metal selected from nickel, cobalt, copper,iron or mixtures thereof, alloyed with aluminum and minor amounts ofadditional stabilizing or promoter metals. These additional metalstypically include metals such as iron, chromium or molybdenum, as deemedappropriate for a particular application. The concentration of a basemetal at the surface of the sponge after leaching will generally belimited by the concentration of the metal introduced at the alloyingstage. Consequently, the enhancement of concentration of a particularlyactive base metal, e.g., nickel and/or cobalt, at the surface of asponge, requires use of major amounts of these metals at the alloyingstage.

A typical Raney® cobalt or nickel catalyst has up to about 95% of theprimary metal, i.e., nickel and/or cobalt. With the price of nickelcurrently averaging over $3.00 per lb. and that of cobalt averagingabout $9.00 per lb., the cost of using such catalysts can beprohibitively expensive, especially in reactions involving inexpensiveorganic reactants and products, such as the conversion of dextrose tosorbitol or the conversion of nitrites to amines, wherein the catalystprice may be considered a significant cost component of the overallprocess.

It is highly desirable to provide sponge-based catalysts having acatalytic activity comparable to conventional nickel- orcobalt-containing sponge catalysts, e.g., a Raney® nickel or Raney®cobalt, which catalysts have a reduced overall content of nickel and/orcobalt, and a high concentration of these metals at the surface of thecatalyst.

SUMMARY OF THE PRESENT INVENTION

The present invention provides novel nickel and/or cobalt containingsponge catalysts, which have an activity and/or selectivity comparableto conventional nickel and/or cobalt sponge catalysts, e.g., Raney®nickel or Raney® cobalt catalysts, but which require a reduced overallcontent of nickel and/or cobalt. Typically, the catalysts of theinvention comprise nickel and/or cobalt coated on at least a portion ofthe surface of a sponge support. Preferably, the sponge supportcomprises at least one metal selected from the group consisting of iron,copper, nickel, cobalt or mixtures thereof. Most preferably, the spongesupport is a Raney® metal alloy-derived sponge support. The catalysts ofthe invention offer the economical advantage of increased concentrationsof expensive nickel and/or cobalt at the surface of the catalystrelative to the concentration of such costly metals in the spongesupport comprising the catalysts.

In a particularly preferred embodiment of the present invention,composite sponge catalysts in accordance with the invention comprise asponge support coated with nickel and/or cobalt wherein the spongesupport comprises at least one metal other than or different from themetal(s) contained in the coating, e.g., as with a nickel sponge supporthaving a cobalt coating deposited thereon. Preferably, the spongesupport comprises at least 50 weight percent of a metal, which isdifferent from the metal(s) contained in the coating. Such a compositionoffers the advantage of efficient and versatile use of metals in thecoating and support to create catalysts having unique characteristics ofcatalytic activity and/or selectivity associated with a mixture ofmetals.

Advantageously, the present invention provides nickel and/or cobaltcontaining sponge catalysts having a reduced overall content of nickeland/or cobalt as compared to conventional nickel and/or cobaltcontaining sponge catalysts, e.g., Raney® nickel or Raney® cobaltcatalysts, while having a high concentration of nickel and/or cobaltmetal at the surface of the catalysts.

The present invention further provides novel nickel and/or cobalt spongecatalysts having a sponge support and a nickel and/or cobalt containingcoating having different characteristics of selectivity and catalyticactivity.

The present invention also provides nickel and/or cobalt plated spongecatalysts having a nickel and/or cobalt concentration at the surface ofthe catalyst which is increased relative to the concentration of nickeland/or cobalt contained in the sponge support comprising the catalyst.

The present invention further provides a method of preparing the nickeland/or cobalt plated catalysts of the invention.

The present invention also provides improved processes for thepreparation of organic compounds using the nickel and/or cobaltcontaining catalysts of the invention.

These and other aspects of the present invention are described infurther detail below.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of this invention, the term “sponge support” is used hereinto mean a porous material which is comprised of metal(s) and has a highsurface area. Surface area can be defined as the total area (twodimensional measurement in square meters) of exposed surface of a solidmaterial whether in the form of fibers, particles, sponges, and thelike. This area includes those areas that are contained inirregularities, cracks and openings of all type, internal and externalto the outermost boundary of the material. The term “porous” is usedherein to describe that portion of the surface internal to the solidstructure of the material. It is within the scope of this definitionthat the porosity may take the form of tortuous pores extendingthroughout the volume of the material. The porous metal materialstypically have a pore volume (nitrogen BET) of at least about 0.05 cc/g;an average pore diameter of at least 20 Angstroms; and a surface area(BET) of at least 5 m²/g, preferably at least 10 m²/g. The porous metalmaterial may be a Raney® metal alloy-derived sponge material or a spongematerial made by other conventional methods sufficient to achieve therequired characteristics of porosity and high surface area, e.g.,reduction of metal oxides or ores (e.g., iron sponge made by the ‘directreduction of iron’ process, available from Reade Advanced Materials,Providence, R.I., or ‘carbonyl iron’ powders available from BASFAktiengeselloschaft, Germany). Where the porous material is a Raney®metal alloy-derived sponge material, the material may also includeresidual aluminum in the form of a solid solution with metals, e.g.,iron, nickel and the like, metal aluminide or hydrous aluminum oxide.

The term “metal(s)” is used herein to mean a chemical element that inits pure form would exist in a condensed state of matter at standardconditions (atmospheric pressure and room temperature), that typicallyforms positive ions when in solution (e.g. acidic solution), and whoseoxides typically form hydroxides rather than acids when in contact withwater. Specific examples of metals include, but are not limited to, theelements of the transition series of the Periodic Table (both basemetals, e.g., iron, copper, nickel, cobalt, molybdenum, chromium, zinc,manganese, etc., and precious metals, e.g., palladium, platinum, etc.),plus main group elements from group IA (e.g., sodium), group IIA (e.g.,magnesium), and group IIIB (e.g., aluminum). An element which is a metalmay occur in more than one species, i.e. in the “metallic form, thefully reduced or zero valent form (e.g. Ni^(o), also known as “nickelmetal”), a component of a metal-containing compound, examples of whichmay include, but are not limited to, oxides, hydroxides, carbonates,sulfates, chlorides, phosphides, borides, aluminides, and the like, or a“partly metallic” form (i.e. containing both the zero valent form andcompounds of the metal). It is within the scope of this definition thatthe compound may be an oxidized form of the metal (e.g. NiO or Ni(OH)₂).The metal-containing compounds may also include a solid solution suchas, for example, aluminum dissolved in metals such as iron, nickel,cobalt and the like. The terms “nickel”, “cobalt”, “iron”, “copper”,“chromium” and the like, as used herein refer to the metal irrespectiveof its form (metallic, oxidized or contained in another compound),unless otherwise specified. Stated percentages of metals in compositionsrecited herein are on a “metals-only basis”.

For purposes of this invention, the deposition process may behereinafter referred to, interchangeably, as “depositing”, “plating”,“coating”, or “dispersing” the nickel and/or cobalt metal(s) onto thesurface of the sponge support.

The catalyst of the invention is comprised of a sponge support having atleast a portion of its surface coated with a metal selected from thegroup consisting of nickel, cobalt and mixtures thereof. In accordancewith one embodiment of the invention, the sponge support comprises atleast one metal other than or different from metal(s) contained in thecoating. For example, when the coating on the support comprises nickel,the sponge support comprises at least one non-nickel metal, such as, forexample, iron, copper, cobalt, aluminum and mixtures thereof. Where thecoating on the support comprises cobalt, the sponge support comprises atleast one non-cobalt metal, such as, for example, iron, copper, nickel,aluminum and mixtures thereof. Preferably, the sponge support comprisesat least 50 weight percent, most preferably at least 60 weight percent,even more preferably at least 80 weight percent, of a metal other thanor different from the metal(s) contained in the coating.

The composition of the invention catalyst may be defined in terms of itstotal nickel and/or cobalt content. The total nickel and/or cobaltcontent depends on the amount of nickel and/or cobalt initially presentin the sponge support, the amount of nickel and/or cobalt depositedduring the plating process, and the amount of weight loss, i.e. bydisplacement or dissolution of metals from the support, by the spongesupport during the plating process. The loss of metals during platingare generally limited mainly to the non-Ni and non-Co metal parts of thesponge support, which may be chemically removed at low to moderatelevels (e.g., less than 20% of the original sponge support weight). Incombination with the nickel and/or cobalt present in the sponge supportand subsequently deposited during plating, these losses affect the final(total) nickel or cobalt content of the plated sponge catalyst.

For example, if a sponge support contains 20% Ni before the addition ofNi at 30% of the original sponge support weight (and assuming 100%transfer of Ni from solution to sponge support, and 10% loss of weightfrom the sponge support during deposition), the final material's % Niis=(20%+30%)/(1.00+0.30−0.10)=about 42%. The additive and subtractiveterms in the denominator of this expression accomplish there-normalization of the total solid material weight. The materialbalance calculation is completed by verifying that the non-Ni part ofthe final material is=(80%−10%)/(1.00+0.30−0.10)=about 58%.

Typically, the plated sponge catalyst of the invention comprises lessthan 98, preferably less than 80, more preferably less than 60, and mostpreferably less than 30, weight percent of nickel and/or cobalt in thetotal catalyst composition. In a particularly preferred embodiment ofthe invention, plated catalysts in accordance with the inventioncomprise from about 8 to about 98, preferably from about 10 to about 60,most preferably from about 15 to about 45, weight percent of nickeland/or cobalt in the total catalyst composition.

Nickel and/or cobalt coated sponge catalysts of the invention have anickel and/or cobalt concentration at the catalyst surface, i.e., theoutermost 50 Å of the catalyst as determined by X-ray PhotoelectronSpectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis(ESCA), which is increased relative to the concentration of nickeland/or cobalt contained in the sponge support comprising the catalyst.For example, where the sponge support is an iron sponge containing minoramounts of nickel, the nickel concentration at the surface of the coatedcatalyst is increased relative to the concentration of nickel containedin the sponge support. Typically, the atomic ratio of the concentrationof nickel and/or cobalt to the concentration of at least one other metalcontained in the support, e.g., iron, at the surface of the inventioncatalyst as measured by XPS or ESCA, is 0.20 or greater, preferably 0.5or greater, most preferably 1.0 or greater, as compared to less than0.10 for an uncoated sponge support. Further, where the support is aRaney® nickel containing residual aluminum, the nickel concentration atthe surface of the coated Raney® nickel catalyst is increased relativeto the concentration of nickel contained in the Raney® nickel support.Similarly, cobalt can be coated on a Raney® cobalt sponge support toenhance cobalt concentration at the surface of the support.

Sponge supports useful in the catalysts of the invention include anyconventional sponge materials. As will be understood by one skilled inthe art, the amount of each metal present in the sponge support willvary, depending on such factors as the intended use of the finalcatalyst, the desired catalytic performance, cost constraints, etc. In apreferred embodiment of the invention, the sponge support comprises atleast 50, more preferably at least 60, and most preferably at least 80,weight percent of metals selected from the group consisting of iron,copper, nickel, cobalt or mixtures thereof. The amount of nickel and/orcobalt in the sponge support will be less than 98, preferably less than40, and most preferably less than 30, weight percent of the support.Typically, the amount of nickel and/or cobalt present in the supportranges from about 0 to about 98, preferably from about 2 to about 40,and most preferably from about 5 to about 30, weight percent of thesupport.

It is also within the scope of this invention that minor amounts (e.g.,less than 40 weight percent, preferably less than about 30 weightpercent, most preferably less than 15 weight percent) of additionalstabilizing or auxiliary metals may be included in the support. Suchadditional metals may include, but are not limited to, metals selectedfrom the group consisting of copper, iron, chromium, titanium, tungsten,molybdenum, zinc, zirconium, manganese, aluminum, vanadium and mixturesthereof. Typically these additional metals are present in the support inamounts ranging from about 40 to about 1, preferably from about 30 toabout 2, most preferably from about 15 to about 3, weight percent of thesponge support.

The sponge support may also contain a precious metal dopant selectedfrom the group consisting of platinum, palladium, iridium, rhodium,osmium, ruthenium, rhenium and mixtures thereof, as described in U.S.Pat. Nos. 6,309,758 and 6,395,403, said references being hereinincorporated in their entirety by reference. Typically the amount of theprecious metal dopant present in the support is less than 1.5,preferably less than 1.0, most preferably less than 0.5, weight percentof the support. In a preferred embodiment of the invention the preciousmetal dopant is present in the support in an amount ranging from about1.5 to about 0.1, preferably from about 1.0 to about 0.5, mostpreferably from about 0.5 to about 0.1, weight percent of the support.

The sponge support will typically have a pore volume (nitrogen—BET)ranging from about 0.05 to about 0.3 cc/g, preferably from about 0.1 toabout 0.2 cc/g, and an average pore diameter ranging from about 10 toabout 500, preferably from about 40 to about 200, Angstroms. The surfacearea (BET) of the sponge support is at least 5 m²/g, preferably at least10 m²/g. In one embodiment of the invention, the surface area of thesponge support ranges from about 10 to 200, preferably from about 20 toabout 150 m²/g. The sponge support may be in any form having ameasurable BET surface area, e.g. particles, monoliths, grids, fibers,plates, and the like. Preferably the support is in the form ofparticles. When used as particles, the median particle diameter of thesponge support is typically less than 500 microns, preferably less than75 microns. When contemplated for use in fixed bed reactions, the medianparticle diameter of the sponge support ranges from about 0.1 to about0.8 cm, preferably from about 0.15 to about 0.5 cm.

In a preferred embodiment of the invention, the sponge support is ametal alloy derived sponge (e.g. a Raney® metal sponge), typicallyformed by partial and selective extraction (or “leaching”, “digestion”)of aluminum and/or silicon from an alloy comprised of aluminum and/orsilicon and at least one other metal such as iron. The precursor to thesponge support is an alloy with an extractable component, namelyaluminum or silicon. Suitable alloys include, but are not limited to,metal-aluminum alloys wherein the metal is selected from the groupconsisting of iron, steel, copper, nickel, cobalt or mixtures thereof.For example, an iron-aluminum alloy is formed by a pyrometallurgical(high temperature melting of metals) process yielding a compositionhaving from about 30 to about 70 weight percent (preferably from about40 to 60 weight percent) aluminum with the remainder consisting mainlyof iron. Smaller amounts of other base metals may, optionally, bepresent as stabilizers for the sponge support and/or finished catalyst,during and after the formation process. Such stabilizers may include,but are not limited to, a metal selected from the group consisting ofnickel, copper, cobalt, chromium, molybdenum, tungsten, manganese,titanium, zirconium, vanadium or zinc, in various combinations, of up toabout 20 percent, preferably less than 15 percent, percent by weight ofthe alloy composition.

When the catalyst is intended for use in a fluidized or “slurry” typereactor, the alloy is formed into a powder typically by crushing andgrinding, but alternatively by atomization (i.e., droplet formation fromthe molten stage), into particles having an median particle size of lessthan 500 micron diameter, preferably less than 75 micron diameter. Thealloy powder is converted to a higher surface area form or “activated”by leaching (extracting) the aluminum from the alloy with an aqueousalkali solution, such as an aqueous solution of sodium hydroxide orpotassium hydroxide. The alkali is used at concentrations of at leastabout 15 weight percent, preferably from about 15 to about 35 weightpercent, and most preferably from about 20 to about 30 weight percent,of the solution. The leaching is carried out at temperatures rangingfrom ambient temperature to elevated temperatures up to the boilingpoint of the leaching solution. Temperatures of from about 40° C. to110° C. (preferably 60° C. to 100° C.) are typical to cause substantialrate of leaching and removal of the aluminum from the alloy.

When the present catalyst is contemplated for use in fixed bed (e.g.packed column type) reactors, the sponge support preferably has a medianparticle size diameter (or largest dimension) of from about 0.1 to about0.8 cm. This is achieved either by crushing and size-classifying (e.g.,sieving) the original alloy, or by forming aggregate bodies by bindingfiner powder into regular shapes, by extrusion or pelletizing and heattreatment. (See U.S. Pat. Nos. 4,826,799 and 4,895,994, which patentsare herein incorporated in their entirety by reference). The alloyparticles or formed particles are leached with an aqueous alkalisolution as described above having an alkali concentration of from about5 to 35 weight percent, preferably from about 10 to about 25 weightpercent of the solution. The leaching is normally carried out atelevated temperatures of from about 30° C. to about 90° C., preferablyfrom about 30° to about 50° C. in the case of crushed alloy particles,and preferably from about 60° to about 90° C. in the case of previouslyheat-treated formed particles. After being leached, sponge support iswashed with water to remove the aluminate by-product. Total removal ofthe aluminate is not required. However, washing is preferably continueduntil the effluent wash water has an alkaline pH of from at least 7 toabout 12. The washing is conducted with water (or a dilute aqueoussolution at modified pH) having a temperature ranging from ambient toabout 60° C., preferably from about 30° C. to about 45° C. It ispreferred that the washing be conducted under an inert (e.g., N₂ or Ar)atmosphere or one having a dilute concentration (2-8%, preferably 3-5%)of hydrogen carried in an inert gas. The method for washing can eitherbe batch type (discontinuous process also sometimes known as‘decantation’, using cyclic addition of a fixed amount of washing liquidfollowed by agitation, separation of solids from liquid, followed byaddition of more liquid as the cycle repeats), or continuous,appropriate for fixed bed catalysts, in which flowing liquid issimultaneously being both introduced and removed.

Plating Process

The catalysts of the invention are prepared by depositing a nickeland/or cobalt coating onto at least a portion of the surface of a spongesupport. The present invention shall hereafter be described, by way ofexample, by the deposition of nickel onto a sponge support made by theRaney® process, wherein the support contains at least 50 weight percentiron. It is understood however, that the process as generally describehereafter is also be effective to coat cobalt, alone or in combinationwith nickel, onto a variety of sponge supports.

Before and during the plating process, it is understood that the spongesupport is protected from air by, for example, keeping it immersed in anaqueous solution, preferably the residual wash solution obtained duringpreparation of the support as described herein above, and maintaining itunder a non-oxidizing atmosphere (noble gas or N₂), and/or sparging asuspension containing the support with a non-oxidizing gas. Hydrogen gasitself, if introduced as fine bubbles and with sufficiently vigorousmixing, is also a useful agent in this process, but primarily to helpmaintain a non-oxidizing environment throughout the process by exclusionof air.

Further, it is to be understood that the deposition process is conductedin a vessel capable of being heated and stirred while being protectedagainst air introduction and evaporative losses of liquid. The contentsof the vessel are being stirred (or in the case of a fixed bed catalyst,the liquid phase is optionally circulated with respect to the stationarysolid phase by pumping) throughout the duration of the process unlessotherwise stated.

The nickel coating may be deposited onto the sponge support using anaqueous plating slurry formed by a mixture of an aqueous slurrycontaining the support and a suitable nickel salt. The aqueous slurrycontaining the support is formed from a mixture of water or an aqueoussolution with the sponge support. Where the support is a Raney® metalalloy derived sponge, the support containing slurry may exist after theleaching and washing steps involved in making the sponge by simplyleaving the sponge in water (optionally adding more water) to protect itfrom air. Alternatively, the support containing slurry may be formedusing a sponge support that is stable in air by placing said supportinto water or an aqueous solution.

The concentration of the sponge support in the aqueous slurry willgenerally range from about 2 to about 15 weight percent of the slurry.Preferably, the concentration of the sponge support in the slurry willrange from about 3 to about 12 weight percent of the slurry, with arange of from about 5 to about 10 weight percent being the mostpreferred.

Prior to the addition of nickel salt to the aqueous slurry containingthe sponge support, the pH of the slurry may optionally be adjusted tomore closely match the final pH of the plating slurry, e.g., pH rangingfrom about 5.0 to about 6.0, and/or to remove surface iron oxide(s) orother metal oxides formed in the leaching and washing steps describedabove in order to form a support surface more receptive to nickeldeposition. This can be achieved by the addition of a suitable acid tothe slurry. For example, sulfuric acid may be added in an amountsufficient to achieve a pH in the range of about 5.5 to about 6.0 priorto adding nickel sulfate to the slurry. The amount and type of acidadded will vary depending on the pH resulting from the prior washingsteps, and on the stability of the support at acid pH. To remove surfaceoxides, oxalic acid or acetic acid, for example, may be used, optionallyat elevated temperature, e.g., about 30° to 60° C., to provide for moreeffective nickel plating.

The nickel salt may be added to the sponge support containing aqueousslurry as a dry powder, or, preferably, dissolved in an aqueoussolution. When adding the nickel salt, the slurry preferably is stirredat a rate sufficient to keep the support particles suspended. The nickelsalt may be added to the slurry all at once or gradually.

The concentration of the nickel salt used will vary depending upon thedesired catalytic activity and the intended catalytic process.Generally, the concentration of nickel salt in the plating slurry willbe that concentration sufficient to provide a catalytically effectiveamount of nickel on the surface of the sponge support. Typically, theconcentration of nickel salt in the plating slurry is that concentrationsufficient to provide at least 10 weight percent, preferably greaterthan about 15 weight percent, of nickel relative to the initial weightof the sponge support in the slurry.

Nickel salts useful to prepare the catalyst of the invention will varydepending upon such factors as cost constraints, solubility in theplating solution, and effectiveness for the intended catalyticapplication (as based on purity requirements and types of anionspresent). In general, however, commonly available acid salts of nickelwill be useful provided that anions introduced by the chosen salt do notcause deactivation or self-fouling of the resulting metal surfaces andcan be sufficiently washed out of the newly-plated catalyst to providethe required catalytic performance. The later-described final washingsteps can be varied in combination with the metal salt choice to affectthis, as an iterative improvement based on performance. Typically,nickel salts will include, but are not limited to, sulfate, chloride,nitrate, acetate, citrate and the like.

A reducing agent is added to the plating slurry to reduce nickel ions insolution to nickel. The choice of reducing agent can be partly based onwhether the electrode potential associated with its half-reaction islarge enough to offset the electrode potential for the half-reaction ofions being reduced to plated metal. In the case of depositing nickelthis would theoretically direct one to use reducing agents withhalf-reactions of greater than about +0.26. In actual practice it is notalways possible to use previously-measured electrode potentials topredict suitability of a given reducing agent for use in this invention,because the conditions of use here may vary from those used in theprevious measurements. In particular the pH of the plating slurry mayalter the effectiveness of reducing agents, depending on whether theyare more compatible in solution with acids or bases, and depending onthe extent to which the redox equilibrium produces or consumes thenon-neutral species H⁺ or OH⁻. Typically, the pH of the plating slurryuseful to prepare the catalyst of the invention is acidic, i.e. lessthan 7, preferably less than 6.

Examples of useful reducing agents include, but are not limited to,salts of formic acid (HCOOH), e.g., sodium formate; salts of othercarboxylic acids, such as oxalic, gluconic, pyruvic, and glyoxilic;carboxylic acids; low molecular weight (e.g. 6 carbon atoms or less)aldehydes; reducing sugars such as glucose, hypophosphite (NaH₂PO₂);borohydride (NaBH₄); aminoboranes such as DMAB; lithium aluminum hydride(LiAlH₄); hydrazine (H₂N—NH₂); and low molecular weight alcohols such asisopropanol and mixtures thereof. Preferred reducing agents include, butare not limited to, formaldehyde (HCHO), sodium hyposphosphite, sodiumformate, gluconate, oxalate, sodium borohydride and mixtures thereof. Atlow pH conditions, the actual species present may include acid forms ofsome reagents in addition to the anionic form, such as hypophosphorousacid, e.g., in addition to the hypophosphite ion. These acids, ratherthan their neutralized salt forms, may be added to the plating mixtureif a pH effective for plating can be achieved. This allows for theoption of fewer reagents and possibly fewer steps in the platingprocess, if other acids used for pH adjustments are omitted.

The reducing agent may be added following addition of the metal salt, oroptionally during the chemical and thermal initiation of the platingprocess. The reducing agent may be added all at once or gradually overtime to initiate and control the plating process. Generally, thereducing agent is used in an amount, as readily determined by theskilled artisan, sufficient to accomplish the desired catalyticperformance. Typically, the reducing agent is added in an amount of atleast the stoichiometric amount necessary for the redox reaction withthe metal ions, e.g., nickel ions, in solution, but it could be used inexcess up to a multiple of several molar equivalents.

If, during the deposition process, the nickel is deposited at a ratewhich tends to unevenly coat the support, a more even coating may oftenbe obtained by including a complexing or chelating agent in the nickelsalt solution to control (i.e., slow) the rate of nickel deposition andobtain a more even coating. A chelating agent may also be beneficial toinhibit any displaced metal ions from re-depositing onto the spongesupport. Suitable chelating agents include, for example, hydroxycarboxylic acids (e.g., lactic acid, maleic acid, citric acid, gluconicacid and tartaric acid) and salts thereof (e.g. sodium potassiumtartrate, also described in the art as “Rochelle salt”), with citric andgluconic acids and salts thereof being particularly preferred.Typically, the chelating agent is added in an amount of at least thestoichiometric amount necessary for the complexation reaction with themetal ions, e.g., nickel ions, in solution, but it could be used inexcess up to a multiple of several molar equivalents.

It is also within the scope of the invention to optionally add one ormore metal stabilizers to the plating slurry. Suitable metal stabilizersinclude, but are not limited to, salts or complexes of metals selectedfrom the group consisting of chromium, titanium, niobium, tantalum,zirconium, vanadium, molybdenum, manganese, tungsten, bismuth, andmixtures thereof. The presence of such stabilizers tends to extend thelife of the catalyst during use, i.e., increase the number of reactionruns in which the catalyst can be used before its activity decreases tounacceptable levels, or increase the shelf life of the catalyst prior touse. The amount of metal stabilizers can vary within wide limitsdepending on desired results. Preferably, however, the totalconcentration of metal stabilizers is less than 10% of the totalcatalyst composition. More preferably, the total concentration of themetal stabilizers is less than 5%.

Prior to initiation of the plating process, the plating slurry willpreferably have a pH within a range that is constrained at its lower endby the beginning of solubility of the sponge support in the platingslurry, and at its upper end by the beginning of the precipitation ofnickel as particles separate from and/or unattached to the support.Typically the pH should be greater than 4.0. Preferably, the pH shouldrange from about 5.0 to about 7.0 depending on such factors as thepresence of chelating or complexing agents and the solubility of thesponge support. Most preferably, the pH at this stage will be that pHwhich naturally occurs upon contact of the nickel salt with the supportand reducing agent without chelating agents present, i.e., from about 5to about 6. As will be understood by one skilled in the art, the pH ofthe plating slurry can be adjusted by the addition of minor amounts ofbase or acid as needed.

Further, prior to initiation of the deposition process, the platingslurry is mixed with agitation for a time sufficient, e.g., about 5 toabout 10 minutes, to ensure uniform distribution of reagents in theslurry.

The nickel coating may be deposited on the sponge support using varioustechniques well known in the art for depositing metal onto metalsurfaces. These techniques include, for example, liquid phase methods,such as electrochemical displacement plating and electroless plating. Aparticular preferred technique of acidic electroless plating, optionallyin combination with electrochemical displacement plating, is describedbelow.

Electroless plating comprises reducing metal ions to metallic or partlymetallic form in a solution in contact with a support wherein all orsubstantially all of the metal ions reduction is accomplished by anexternal reducing agent rather than the support itself. In the presentinvention, electroless plating of the nickel coating on the support isaccomplished by adjusting the pH and temperature to ranges where thereducing agent is effective to deposit all or substantially all of thenickel metal onto the support. Electroless plating may be accomplishedby adjusting the pH of the aqueous plating slurry to about 5.5 to about7, preferably about 5.5 to about 6.0, by the addition of aqueous acid(such as acetic or sulfuric acid) or base (such as sodium hydroxide orammonia), and subsequently, adjusting the temperature of the slurry toat least 30° C. Preferably, the temperature is adjusted to be within arange of about 50° C. to about 90° C.; most preferably the temperatureis adjusted to within a range of about 60° C. to about 85° C.

It is also contemplated that the plating process may optionally beaccomplished hydrothermally, i.e., under applied pressure to achieve atemperature of greater than 100° C.

Where the metals of the sponge support are less stable, i.e., moreeasily oxidized under the plating reaction conditions than the metals inthe coating, electrochemical displacement plating may optionally befirst used to initiate the deposition process, followed by electrolessplating as herein described above to complete the deposition. Likeelectroless plating, displacement plating involves reducing metal ionsin solution to metal. However, unlike electroless plating, inelectrochemical displacement plating, substantially all the metal ionsreduction which occurs is accomplished by metals of the support. In thepresent invention, the electrochemical displacement plating process maybe accomplished by adjusting the pH of the plating slurry to about 5 (byaddition of a small amount of acid, such as acetic or sulfuric acid),and maintaining such a pH for a time sufficient to initiate thedisplacement of support metal, e.g., iron, with deposition of nickelfrom the plating slurry. Typically, the pH is maintained at this levelfrom about 5 to about 10 minutes.

The amount of time for completion of the plating process will varydepending upon such factors as the temperature, pH and type of support.Generally, the plating process proceeds for an amount of time sufficientto effect deposition of all or substantially all of the nickel in theplating slurry on the support surface. In a preferred embodiment of theinvention, the plating process is conducted for a time sufficient toprovide a nickel coating comprising from about 10 to about 60 grams,preferably from about 15 to about 50 grams, even more preferably fromabout 20 to about 45 grams, of nickel per 100 grams of the spongesupport. Typically, the plating time ranges from about 20 minutes toabout 2 hours.

At relatively high loadings of nickel (i.e., greater than about 25weight percent of the support), it is preferable to apply themetal-containing coating in multiple plating operations. Preferably, themultiple coating is applied in successive plating operations. Further,maintaining high porosity in the product and removal of byproduct saltsand residues may be aided by using two or more separate platingoperations at lower metal concentrations, separated by washing steps.

For example, a nickel loading in a first plating process ranging fromabout 5 to about 20 weight percent relative to the sponge supportweight, followed by a nickel loading in a second plating operationranging from about 5 to about 20 weight percent relative to the weightof the sponge support, may be used to provide a combined nickel contentof from about 10 to about 40 weight percent nickel on the surface of thesponge support. In between successive plating operations, the agitationof the plating slurry is preferably discontinued and support particlesare separated from spent plating solution using a conventionalsolid-liquid separation process, e.g., filtration or settling. Solidsresulting from a prior plating process are preferably washed asdescribed herein above for the preparation of the support, either withwater or dilute aqueous solutions of base or acid depending upon theresidues to be removed, optionally at elevated temperature, e.g., fromabout 40° C. to about 60° C. The dilute aqueous solutions of base oracid for washings may be chosen for their effectiveness in removingparticular types of residues, e.g., they may contain ions capable ofdisplacing or removing targeted residues: alkali metal hydroxides beingcapable of displacing H⁺ ions; chelating anions such as oxalate,citrate, etc. being capable of removing metal cations. Subsequentplating processes are achieved essentially by repeating the abovedescribed steps, including addition of nickel salt and other reagents,or optionally pre-treatment with acid prior to plating. All of theoptional process variations described hereinabove may be varied asdesired in the subsequent plating procedure.

Following completion of deposition, the nickel coated porous spongecatalyst is removed from the spent plating slurry by conventionalsolid-liquid separation process, e.g., filtration or settling, and isthereafter washed, with water or optionally an aqueous alkaline solution(e.g., NaOH), for a time and at a temperature sufficient to neutralizeand/or remove substantially all acid residues and salts.

The washed nickel coated sponge catalyst may be treated at this point toadd a metal promoter followed by washing as described above. Suitablemetal promoters, include, but are not limited to, metals selected fromthe group consisting of chromium, molybdenum, titanium, zinc, vanadium,zirconium, or mixtures thereof. The metal promoters may be deposited onthe surface of the catalyst in the form of a metal in its zero valentstate or in an oxidized state. The promoters may be present in amountsup to 3.0, preferably up to 2.5, most preferably up to 2.0, weightpercent of the catalyst. Preferably, the promoter is present in thecatalyst in the range of from about 0.2 to about 3, most preferably fromabout 0.3 to about 2, even more preferably from about 0.5 to about 1,weight percent based on the weight of the catalyst. The promoter metalsmay be added by conventional processes using a metal salt solution(e.g., Mo can be added using a molybdate salt, or Cr using a chromatesalt).

The promoted or unpromoted plated catalyst may also be doped with aprecious metal dopant selected from the group consisting of platinum,palladium, iridium, rhodium, osmium, ruthenium, rhenium and mixturesthereof as described in U.S. Pat. Nos. 6,309,758 and 6,395,403, saidreferences being herein incorporated in their entirety by reference,followed by washing as described above. Typically the amount of theprecious metal dopant present in the catalyst is less than 1.5,preferably less than 1.0, most preferably less than 0.5, weight percentof the catalyst. In a preferred embodiment of the invention the preciousmetal dopant is present in the catalyst in an amount ranging from about1.5 to about 0.1, preferably from about 1.0 to about 0.1, mostpreferably from about 0.5 to about 0.1, weight percent of the catalyst.

The final catalyst is normally stored as an aqueous slurry until use.Following washing, the plated catalyst can optionally be separated fromthe final wash solution and stored in an alcohol (e.g. C1-C3 alkanol) orwater-alcohol medium.

Composite sponge catalysts of the invention uniquely provide on thesurface of a sponge support a nickel and/or cobalt coating having adifferent catalytic characteristic from the metals comprising thesupport, e.g., a nickel-based sponge support having a cobalt coatingdeposited thereon. The ability to provide such a variation in thesupport and coating enables the efficient and versatile use of metals inthe coating and the sponge support to create composite catalysts havingthe unique properties associated with a mixture of metals. For example,a catalyst having the selectivity and activity characteristics of bothnickel and copper may be prepared by depositing nickel onto a coppercontaining sponge support.

Plated porous base metal catalysts of the invention are useful in thepreparation of organic compounds from corresponding precursor organiccompounds using catalyzed chemical processes such as hydrogenations,dehydrogenations, reductive alkylations, aminations, and organiccoupling reactions. Thus, in general, the plated catalysts of theinvention are useful in processes commonly catalyzed by sponge metalcatalysts such as Raney®Ni and Raney®Co, or Ni or Co catalysts in whichthe active metals are supported on conventional metal oxide supports(e.g., Ni/silica or Co/alumina). It is further contemplated thatcomposite catalysts of the invention, e.g., cobalt coated iron basedsponge catalysts, are useful to catalyze Fischer-Tropsch synthesis inwhich CO is reacted with hydrogen to make hydrocarbons, as described inH. Schulz, “Short History and Present Trends of Fischer-TropschSynthesis”, Applied Catalysts. A, v. 186, pp. 3-12 (1998). Othercompositions such as highly Mo-promoted modifications of Co/Fe and Ni/Femay be useful in hydrotreating applications to remove sulfur, nitrogenand phosphorus compounds and heavy metals from petroleum feedstocksprior to further processing the feedstocks into useful fuels, asdescribed in R. J. Farrauto and C. H. Bartholomew, Chapter 9 ofFundamentals of Industrial Catalytic Processes, pp. 523-535, pub:Blackie Academic & Professional, 1997. The novel materials of thisinvention may also have utility in other applications wherehydrogenation catalysts are used with a benefit of reduced costs for theuser, e.g., a method for the adsorptive removal of sulfur fromhydrocarbons as described in U.S. Ser. No. 09/833,602, filed Apr. 13,2000, Schmidt, et al., and a method for the preparation of electrodecomponents in fuel cells or hydrogen generators as described in JapanesePatent Application No. 01126738, and U.S. Pat. No. 3,634,140.

In a preferred embodiment of the invention, the plated catalysts of theinvention are useful to accomplish more economical catalytichydrogenation processes when compared to hydrogenation processes carriedout using conventional porous sponge catalysts, such as, for example, aRaney®nickel catalyst. Examples of such reactions are described inSkeleton Catalysts in Organic Chemistry by B. M. Bogoslawski and S. S.Kaskowa and in Use of Nickel Skeleton Catalyst in Organic Chemistry VEBDeutsches Verlag der Wissenschaften, Berlin 1960, pg. 40-124, theteachings of which are incorporated herein in their entirety byreference. In particularly, the invention catalysts are useful in ahydrogenation reaction wherein the sugar dextrose, an “aldose”(containing the unsaturated aldehyde group) is the feedstock that isconverted to sorbitol, a sugar alcohol useful as a food additive and asan intermediate in pharmaceutical synthesis. As an optional feature ofthe various catalyzed chemical processes in which catalysts of theinvention may be used, further reduction of the coated nickel or cobaltmay be practiced as needed. This further reduction may be achievedeither prior to adding the catalyst to the catalytic process reactor,e.g., by treatment with hydrogen gas or a chemical reducing agentsolution, or preferably in a hydrogenation process may be achieved underapplied hydrogen pressure “in situ” prior to or during the early stagesof the process.

The final catalyst may also contain trace amounts of phosphides,borides, carbonates, and the like, as compounds of the plated nickeland/or cobalt, or similar residues incorporated during the platingprocess, depending on the type and degree of decomposition of thereducing agents employed during the deposition process. This may in turnaffect the suitability of the resulting material for specific catalyticapplications such as the hydrogenation of certain types of organiccompounds (e.g., nitrites when hydrogenated to amines).

To further illustrate the present invention and the advantages thereof,the following specific examples are given. The examples are given asspecific illustrations of the claimed invention. It should beunderstood, however, that the invention is not limited to the specificdetails set forth in the examples.

All parts and percentages in the examples, as well as the remainder ofthe specification, which refers to solid compositions or concentrations,are by weight unless otherwise specified. However, all parts andpercentages in the examples as well as the remainder of thespecification referring to gas compositions are molar or by volumeunless otherwise specified.

Further, any range of numbers recited in the specification or claims,such as that representing a particular set of properties, units ofmeasure, conditions, physical states or percentages, is intended toliterally incorporate expressly herein by reference or otherwise, anynumber falling within such range, including any subset of numbers withinany range so recited.

EXAMPLES

Analytical and performance parameters recited in the Examples aredefined as follows:

The average surface concentration of a deposited metal was compared tothe average surface concentration of a metal contained in support, andexpressed as an atomic ratio, e.g., Ni/Fe in a nickel coated sponge ironsupport. Ni/Fe and other atomic ratio values as recited in the Exampleswere determined using XPS or ESCA methods as described in U.S. Pat. Nos.6,395,403 and 6,309,758, within a surface depth of the outermost 50 Å ofa catalyst material and are an average of ratios catalyst particlesmeasured simultaneously.

Productivity values as recited in the Examples were determined by therate at which dextrose was converted to sorbitol using a given amount ofcatalyst. One defined measure of productivity, which is the amount of agiven product made per unit time per unit weight of catalyst in a batchprocess run to complete conversion of feedstock to product, wascalculated as follows:

${Productivity} = \frac{{Weight}\mspace{14mu}{Product}}{\left( {{Batch}\mspace{14mu}{completion}\mspace{14mu}{time}} \right)\left( {{Weight}\mspace{14mu}{catalyst}} \right)}$

When the operating conditions of the batch test are fixed (i.e., weightof feedstock, temperature, and pressure, plus weight of catalyst or‘catalyst loading’ are all held fixed), a series of catalysts tested atthese conditions can be compared in productivity by the simple ratio oftheir batch completion times. For example, for any given experimentalcatalyst relative to the catalyst designated as the ‘standard’,productivity may be calculated as follows:

${{Productivity}\mspace{14mu}{ratio}} = {\frac{{Productivity}\mspace{14mu}({experimental})}{{Productivity}\mspace{14mu}({standard})} = \frac{{Batch}\mspace{14mu}{{compl}.\mspace{14mu}{time}}\mspace{14mu}({standard})}{{Batch}\mspace{14mu}{{compl}.\mspace{14mu}{time}}\mspace{14mu}({experimental})}}$

The productivity ratio can be refined to allow for comparison ofcatalysts having very different active metal contents. This methodincludes cost efficiency in the evaluation, since (as is the case herewith Ni or Co) the active metal component may also be the most expensivemetal among the raw materials (based on cost multiplied by total amountused). If the total weight of catalyst is still fixed, but the activemetal content (Ni, in this example) differs between the experimental andstandard catalysts), the productivity ratio may be calculated as:

$\frac{{Productivity}\mspace{14mu}({experimental})}{{Productivity}\mspace{14mu}({standard})} = \frac{\left\lbrack {{Batch}\mspace{14mu}{{compl}.\mspace{14mu}{Time}}\mspace{14mu}({std})} \right\rbrack \times \left\lbrack {{Ni}\mspace{14mu}{content}\mspace{14mu}({std})} \right\rbrack}{\left\lbrack {{Batch}\mspace{14mu}{{compl}.\mspace{14mu}{Time}}\mspace{14mu}\left( \exp \right)} \right\rbrack \times \left\lbrack {{Ni}\mspace{14mu}{content}\mspace{14mu}\left( \exp \right)} \right\rbrack}$

This ratio based on Ni content only becomes a relevant discriminator forranking the value of catalysts with comparable (relatively short)absolute batch times. The first requirement of the catalyst is usuallythat it perform adequately, and a secondary requirement is cost(proportional to Ni content). Thus, e.g., if an experimental catalystwith 50% Ni content yields a batch completion time of 80 minutes while astandard catalyst with 95% Ni content yields a batch time of 75 minutes,the Ni-based productivity ratio for the experimental vs. standard is:

$\frac{75 \times 95}{80 \times 50} = 1.78$

That is, the experimental catalyst is much more efficient (i.e., 1.78times better) on the basis of Ni employed, although its absolute batchtime is slightly longer.

Surface area measurements recited in the Examples were measured by BETnitrogen adsorption method. BET uses an adsorption model and relatedequation to calculate surface area from adsorbed volumes of nitrogen atchosen partial pressures. A particular application of BET surface areameasurement is described in S. R. Schmidt, “Surfaces of Raney®Catalysts” in Catalysis of Organic Reactions, eds. M. G. Scaros and M.L. Prunier, pub. Marcel Dekker, 1995.

Bulk chemical analysis of the compositions prepared in the Examples wasanalyzed by Inductive Coupled Plasma-Atomic Emission Spectroscopy(“ICP”). Each sample was washed with water and then completely dissolvedin a mixture of HCl/NHO₃ acid (3:1) solution prior to analysis.

Amounts of metals indicated in compositions of the finished catalystsrecited in the Examples are on a metals only basis. The sum of theanalyzed metals was normalized to 100%, i.e. amounts of non-metalelements, e.g., oxygen, carbon and hydrogen, were not included. In caseswhere the stated metal percentages total to slightly less than 100%, theunstated remainder of the metal composition consists of unintended tracecontaminants.

Example 1

An Fe and Ni containing sponge support was prepared as following:

An alloy was made by mixing 60 parts (by weight) of Al, 27 parts of Fe,11 parts of Ni and 2 parts of Mo, and then melting them by heating to amaximum temperature of 1550° C., which was maintained for 20 minutes.The melt was poured onto a graphite-cooling slab where it hardenedwithin a few minutes to about 0.5-0.75″ thickness.

Subsequently, the alloy slab was broken into smaller pieces and reducedin size to <¼″ pieces with a jaw crusher. The crushed material was thenground to a powder using a hammer mill (Micropul). The median diameterof the powdered alloy thus obtained was 31 microns.

Three Hundred (300) g of this powder was added gradually with stirringto a 25% aqueous solution of NaOH (486 g solid NaOH dissolved in 1458 gwater). The peak temperature during this alloy addition stage (48minutes duration) was 90° C. This temperature was maintained byexternally applied heating of the agitated slurry of digestingalloy/catalyst for another 3 hours.

After agitation and heating were stopped and the catalyst support wasallowed to settle, the byproduct solution of sodium aluminate wasremoved by decantation. The catalyst support was then washed bydecantation method (1. add water, 2. stir, 3. settle, 4. decant) forseveral times using ˜45° C. water, stopping when the pH of the spentwash water was 9.0.

Example 2

A Ni plated sponge catalyst was prepared using the sponge support asprepared as described in Example 1 above. An aqueous slurry containingforty (40) grams of the Fe—Ni sponge prepared in Example 1 in 500 ml ofwater was placed in a glass vessel fitted with a stirrer and externalheating mantle. A Ni containing solution was then made by dissolving35.1 g of Ni sulfate hydrate (FW 262.8), an amount sufficient to providea Ni content equivalent of 8 g or 20% Ni relative to the originalsupport weight) in 500 ml water. This solution was then added to theaqueous slurry in the glass mixing vessel and the mixture was stirredfor 10 minutes.

A mixture of two reducing agents (34 g Na formate, FW 68, and 53 gNaH₂PO₂.H₂O, FW 106) was dissolved in 400 ml water). The pH of thissolution was then adjusted to 5.5 by addition of 3M acetic acid. Theadjusted solution was then added to the aqueous slurry and the mixturewas stirred for 5 minutes. The pH of the mixture was then furtheradjusted to 5.0 with acetic acid and mixed for 5 additional minutes.

Next the pH of the aqueous slurry was adjusted upward to 5.5 by additionof 10% NaOH solution and the mixture was heated to 70° C. Stirring wascontinued for 30 minutes at this temperature to complete the firstplating step.

Agitation was then discontinued and the catalyst was allowed to settle.The plating solution was removed by decantation and the catalyst waswashed twice with 2 L of 45° C. water.

The above steps starting with the addition of the Ni sulfate wererepeated except that the amount of Ni sulfate used was 26.2 g (an amountsufficient to provide 15% Ni relative to initial support weight). Thewashing steps after this second plating used (a) 2 L of 5% NaOH solutionat 45° C., (b) 2 L of 5% NaOH solution at room temperature, and (c)repeated 2 L portions of water at 45° C. until a pH of 10.5 was reached.

The surface of the Ni-plated catalyst was promoted with Molybdenum byadding 0.88 g of ammonium heptamolybdate (FW 1235.9) dissolved in 50 mlof water, and then stirring for 30 minutes. Final washing was done withwater at 45° C. to reach a pH of 9.5.

The composition of the resulting catalyst was 49.7% Fe, 44.8% Ni, 3.4%Al and 2.0% Mo.

Example 3

A Ni plated sponge catalyst was prepared as described in Example 2except that the temperature in the plating steps was 85° C. Thecomposition of the resulting catalyst was 49.6% Fe, 44.6% Ni, 3.8% Aland 2.0% Mo.

Example 4

A Ni plated sponge catalyst was prepared as described in Example 2except the temperature in the plating steps was 50° C. The compositionof the resulting catalyst was 51.0% Fe, 43.8% Ni, 3.2% Al and 2.0% Mo.

Example 5

A Ni plated sponge catalyst was prepared as described in Example 2except that the amount of nickel sulfate used in the two successiveplating steps was sufficient to provide 20% Ni each time for an overallnominal Ni plating loading of 40%. The composition of the resultingcatalyst was 50.4% Fe, 44.4% Ni, 3.3% Al and 1.9% Mo.

Example 6

A Ni plated sponge catalyst was prepared as described in Example 2except that the amount of nickel sulfate used Ni loading in the twosuccessive plating steps was reduced to an amount sufficient to provide15% Ni each time for an overall nominal Ni plating loading of 30%. Thecomposition of the resulting catalyst was 55.0% Fe, 39.4% Ni, 3.6% Aland 2.0% Mo.

Example 7

A Ni plated sponge catalyst was prepared as described in Example 2except that only the 53 g of NaH₂PO₂ was employed as reducing agent ineach plating step, omitting Na formate. The composition of the resultingcatalyst was 52.3% Fe, 42.1% Ni, 3.6% Al and 1.9% Mo.

Example 8

A Ni plated sponge catalyst was prepared as described in Example 3except that a sponge support having a Ni content of 12.9%, a Mo contentof 1.7% Mo and an Fe content of 77.8% was used. The composition of theresulting plated catalyst was 57.2% Fe, 35.1% Ni, 5.7% Al and 1.8% Mo.

Example 9

A Ni plated sponge catalyst was prepared as described in Example 3except that a sponge support having a lower Ni content of 12.5%, and anFe content of 77.7%, but no Mo was used. The composition of theresulting plated catalyst was 53.5% Fe, 38.4% Ni, 7.2% Al and 0.8% Mo.

Example 10

A Ni plated sponge catalyst was prepared as described in Example 2except that the reducing agent in each plating step was 68 g of Naformate (2× that of Example 3) and omitting Na hypophosphite. Theresulting catalyst had a composition of 47.8% Ni, 37.6% Fe, 10.1% Al and4.3% Mo.

Example 11

A cobalt plated sponge catalyst was prepared as described in Example 2except that a sponge support having a lower Ni content of 12.5%, and anFe content of 77.7%, but no Mo was used, and cobalt sulfate (FW 281.1)at 37.5 g and 28.2 g, respectively, in the plating steps was usedinstead of Ni sulfate. The composition of the resulting catalyst was31.0% Co, 52.8% Fe, 9.1% Ni, 6.3% Al, and 0.8% Mo. The catalyst had aBET surface area of 62 m²/g.

Example 12

A Cu-based sponge support was made from an alloy with a composition of48% Cu, 2% Cr, and 50% Al by leaching Al at 90° C. in 25% NaOH solutionfor 1 hour. The sponge support had a composition of 90.8% Cu, 4.9% Al,3.4% Cr and 0.6% Ni, and a BET SA of 46 m² g. The sponge support wasplated with Ni using the nickel sulfate amounts of Example 6, but at 85°C. The resulting catalyst had a composition of 73.0% Cu, 4.1% Al, 2.9%Cr, 18.6% Ni, and 0.4% Mo, a BET SA of 50 m²/g. and an XPS Ni/Cu ratioof 3.8.

Example 13

A Ni plated sponge catalyst was prepared as described in Example 7except that a chelating agent, 40 g of citric acid, was used in theplating solutions instead of acetic acid, and the pH for the platingsteps was adjusted to 5.5 with dilute NaOH solution. The resultingcatalyst had a composition of 3.6% Al, 43.3% Fe, 5.9% Mo and 47.2% Ni.The measured BET SA was 84 m²/g.

The analyzed metals remaining in solution after plating were 0.33% Feand 0.39% Ni for the first plating a 0.29% Fe, 0.36% Ni for the secondplating. These levels of dissolved Fe and undeposited Ni are much higherthan normally observed (levels of less than about 0.06% each weretypically observed in Examples 2-10), due to the effect of the optionalchelating agent.

Example 14

A cobalt-plated nickel sponge catalyst was prepared as described inExample 11 using a Raney® Ni, Grade 6800, obtained from Grace Davison,Chattanooga, Tenn. The resulting catalyst had a composition of 14.4 Co,3.2% Al, 81.4% Ni, and 0.6% Mo, a BET surface area of 50 m²/g, and anXPS Co/Ni ratio of 3.8.

Example 15

Testing for the baseline of performance in converting dextrose tosorbitol using Mo/Ni sponge catalyst as the standard was conducted asfollows:

Raney® Ni grade R-3111 was obtained from Grace Davison, Chattanooga,Tenn. A catalyst loading of 6.6 weight percent was used, relative to thedextrose (weight of dry solid equivalent) contained in the reactionmixture. This equated to an actual catalyst weight of 12.3 g and anapparent (underwater) catalyst weight of 10.5 g. The underwater weightwas determined by comparing the weight of a fixed volume of slurry(catalyst plus water) to the weight of the same volume of water alone.The weight difference was then multiplied by a density-based correctionfactor of 1.17 to yield actual catalyst weight. The reaction mixture was272 g of a 68% dextrose (dry solid equivalent) feedstock combined withan additional 228 g of water to make an overall 37% solids solution. Thefeedstock had approximately a 97% dextrose equivalent or DE assay on adry basis, and was obtained from Arancia-CPC of Guadalajara, Mexico.

The 37% solution was heated to about 80° C. and stirred to homogeneity,then combined with the catalyst which had been previously weighed underwater and charged to the empty 1-L autoclave reactor as an approximately50% slurry.

The autoclave was sealed, purged of air using nitrogen 3× (pressurizedto 100 psig, then released, and then purged 3× and filled with hydrogen(99.999% purity, Air Products) by displacing the nitrogen 3×. Hydrogenwas then delivered from a reservoir (pressure bomb) at an initialpressure of about 1000 psig through a pressure regulator to maintain anoperating pressure in the reactor of 700 psig throughout the run. Thetemperature was raised to 140° C. by externally applied electricalresistive heating. The agitation speed was 1900 RPM.

The batch time was monitored starting from when an internal thermocoupleindicated the operating temperature had been reached (t=0). Samples (˜2mL) of reaction mixture were removed periodically (at t=60′, 70′, etc.)by opening a valve, which allowed liquid to be forced through a sinteredmetal type filter within the reactor and then out through a steel tubeto an external sample vial. The reaction was typically allowed tocontinue beyond the time expected for completion, with subsequentquantifying of completeness of reaction, and efficiency in reaching thisendpoint, described as follows.

After a reaction mixture sample was cooled to ambient temperature it wasanalyzed for residual dextrose content by a Biolyzer unit (from Kodak,now available from Johnson and Johnson Ortho Clinical Diagnostics),which uses a calorimetric end point determined with dry chemical slidesto quantify dextrose (glucose) content. This method had previously beencalibrated to indicate an endpoint corresponding to conversion of 99.7%of the dextrose originally present. The time at which the endpoint wasreached was recorded as the batch time for the catalyst being tested.

Testing: (1-a) The Raney 3111 catalyst thus tested yielded a first-cyclebatch time of 75 minutes. This is the standard baseline for productivitycalculations in testing at these conditions.

In this and the subsequent Examples, in the event that a catalyst was‘recycled’ for testing of its durability (retention of productivity),the catalyst contained in the reactor was allowed to settle aftercooling, stopping agitation, and depressurizing the reactor system. Thenthe sorbitol product was removed by pumping it away without disturbingthe settled catalyst.

A new solution of dextrose in water was then added to the reactor andthe test procedure was repeated as described above. This method may berepeated an arbitrary number of ‘cycles’ (batch tests). A catalyst'sbatch time for a given cycle may be compared both to the 1^(st) cyclebatch time for the same catalyst (to indicate rate of deactivation orloss of by the catalyst) and to the corresponding cycle's batch time foranother catalyst (for ranking absolute batch times at equal catalystage).

Testing: (1-b) Re-testing of the std. R 3111 performed at a lowercatalyst loading of 7.6 g apparent weight (8.9 g true weight) equivalentto 4.8 weight percent loading vs. dextrose solids. The catalyst wasrecycled 3 times for a total of 4 test cycles. The batch completiontimes were 75, 75, 85 and 95 minutes. This equates to cycle time ratios(vs. first, shortest cycle) of 1.00, 1.07 and 1.27 for cycles 2-4.

Testing: (1-c) Re-testing of the std. R 3111 performed again at acatalyst loading of 10.3 g apparent weight (12.0 g true weight), butwith 50% dextrose solution, equivalent to 4.8 weight percent loading vs.dextrose solids. The catalyst was recycled 2 times for a total of 3 testcycles. The batch completion times were 80 minutes for all three cycles.This equates to cycle time ratios (vs. first, shortest cycle) of 1.00and 1.00 for cycles 2-3.

Example 16

Ni plated sponge catalysts as prepared in Examples 1-10 were tested forsorbitol production using procedures of Testing (1-a), (1-b) and (1-c)as described in Example 14. Results are recorded in Table 1 below.

TABLE 1 Raney ® Ni and Ni-Plated Catalyst Testing Results BatchCompletion Times Cycle 1 Cycle 1 Cat. Loading (min) Productivity Prod.Ratio Example % Dextrose (wt %) Cycle 1 Cycle 2 Cycle 3 Ratio vs. % Ni15 (1a) 37 6.6 75 1 (std) 1 (std) 15 (1b) 37 4.8 75 75 85 1 (std) 1(std) 15 (1c) 50 4.8 80 80 80 1 (std) 1 (std) 2 37 6.6 80 80 0.94 2.0 237 4.8 80 85 95 0.94 2.0 2 50 4.8 80 80 80 1.00 2.1 3 37 4.8 75 1.00 2.14 37 4.8 85 85 0.88 1.9 5 37 4.8 80 120 0.94 2.0 6 37 4.8 80 0.94 2.3 737 4.8 80 0.94 2.1 8 37 4.8 90 0.83 2.2 9 37 4.8 80 0.94 2.3 10  37 4.880 0.94 1.9

Comparative Example 1

For comparative purposes, sponge catalysts A, B and C having reducedamounts of Ni and increased amounts of Fe as compared to conventionalRaney Ni catalyst were prepared using the alloys as described below. Nodeposition of Ni was performed on the finished sponge catalyst. Thefinished catalysts were tested to determine productivity for convertingdextrose to sorbitol.

Catalyst A: An alloy containing 50% Al, 27.5% Ni, 5% Mo and 17.5% Fe wasmade and then activated as described in Example 1. The resulting spongecatalyst had a Ni content of 52%. The catalyst was tested at theconditions of Example 15(b). The Ni/Fe atomic ratio of the catalyst wasdetermined by XPS. Results are recorded in Table 2 below.

Catalyst B: An alloy containing 50% Al, 21.3% Ni, 7.5% Mo and 21.2% Fewas made and then activated as described in Example 1. The resultingsponge catalyst had a Ni content of 42%. The catalyst was tested at theconditions of Example 15(b). The Ni/Fe atomic ratio of the catalyst wasdetermined by XPS. Results are recorded in Table 2 below.

Catalyst C: An alloy containing 50% Al, 17.5% Ni, 5% Mo and 27.5% Fe wasmade and then activated as described in Example 1. The resulting spongecatalyst had a Ni content of 35%. The catalyst was tested as describedin Example 15(b). The Ni/Fe atomic ratio of the catalyst was determinedby XPS. Results are recorded in Table 2 below.

Comparative Example 2

For comparison purposes, various sponge supports were tested todetermine productivity for converting dextrose to sorbitol withoutdeposition of Ni on the surface of the support. A sponge supportcontaining (A) 24% Ni, as employed in Examples 2-7, and a supportcontaining (B) 13% Ni, as employed in Example 8, were tested for onecycle each at the conditions of Example 15(b), yielding, respectively,batch completion times of 110 and >>120 minutes (incomplete at 120minutes). These equate to productivity ratios of 0.68 and <<0.63,respectively. The catalyst was characterized for Ni/Fe atomic ratio byXPS. Results are recorded in Table 2 below.

Comparative Example 3

For comparison purposes, a Ni plated sponge catalyst was prepared usinga chemical reducing agent but at high pH. The sponge support employedhad a Ni content of 23.4%, 58.7% Fe and 2.8% Mo. The plating wasaccomplished using a 1-hour duration at 60° C., and as plating solutionreagents the equivalent of 20% Ni (relative to support weight) in theform of NiCl₂-6H₂O, a 1.85:1 weight ratio of Na₄EDTA to support, and0.42:1 weight ratio of NaH₂PO₂—H₂O to support. Analyses before and afterthe plating process showed no significant deposition of Ni under theseconditions. Testing as described in Example 15(b) failed to complete thebatch conversion even after 150 minutes. Productivity results and Ni/Featomic ratios are recorded in Table 2 below.

TABLE 2 Ni Content Batch Time Productivity Example No. (%) (min) RatioXPS Ni/Fe Comparative 1A 52 105 0.71 0.22 Comparative 1B 42 120 0.620.12 Comparative 1C 35 140 0.54 0.16 Comparative 2A 24 110 0.680.01-0.03 Comparative 2B 13 >>120 <<0.63 NA Comparative 3 49 >150 <0.5 345 75 1.0 6 39 80 0.94 0.54 9 38 80 0.94

As shown in Table 2, catalysts prepared in Comparative Example 1 fromprecursor alloys containing Ni and having no Ni plating exhibited alower catalyst performance when compared to the performance of catalystsof the invention in Examples 3, 6 and 9. The lower catalyst performancewas also evident in Comparative Example 2 where the precursor alloys hadan increased Fe concentration and a reduced Ni concentration.

Table 2 also showed that the Ni plated sponge catalyst of ComparativeExample 3, prepared by a plating process that employed a high pH with achemical reducing agent, had a low catalyst performance when compared tocatalysts prepared in accordance with the process of the presentinvention.

Comparative Example 4

For comparison purposes, a Ni plated catalyst was prepared as describedin Example 4, with the exception that the pH during the plating was 5.8and no reducing agent was added. The resulting catalyst had a Ni contentof 48.7%, 44.1% Fe, 4.5% Al and 2.6% Mo. The resulting catalyst wastested as described in Example 15(b). Testing failed to complete thebatch conversion even after 150 minutes.

1. A method of preparing a nickel and/or cobalt plated sponge catalystcomprising (a) preparing an aqueous slurry containing a sponge supporthaving surface area; (b) adding to the aqueous slurry a salt of a metalselected from the group consisting of nickel, cobalt and mixturethereof, in an amount sufficient to deposit a catalytically effectiveamount of the metal on at least a portion of the surface area of thesponge support and to form a plating slurry containing ions of metal;(c) adding a reducing agent to the plating slurry in an amountsufficient to reduce the metal ions in the slurry to the correspondingmetal; (d) adjusting the pH and temperature of the plating slurry in amanner sufficient to deposit the metal on the surface of the support andform a metal coated sponge catalyst; and, (e) removing the catalyst fromthe plating slurry.
 2. The method of claim 1 wherein the metal salt isselected from the group consisting of sulfates, chlorides, nitrates,acetates, citrates, and mixtures thereof.
 3. The method of claim 1wherein the concentration of sponge support in the aqueous slurry ofstep (a) ranges from about 2 to about 15 weight percent of the slurry.4. The method of claim 3 wherein the concentration of sponge support inthe aqueous slurry ranges from about 3 to about 12 weight percent of theslurry.
 5. The method of claim 4 wherein the concentration of spongesupport in the aqueous slurry ranges from about 5 to about 10 weightpercent of the slurry.
 6. The method of claim 1 wherein theconcentration of metal salt added to the slurry is a concentrationsufficient to provide at least 10 weight percent of metal relative tothe weight of the support.
 7. The method of claim 6 wherein theconcentration of metal salt added to the slurry is a concentrationsufficient to provide greater than 15 weight percent of metal relativeto the weight of the support.
 8. The method of claim 1 furthercomprising adjusting the pH of the aqueous slurry to range from about 5to about 6 prior to addition of the metal salt.
 9. The method of claim 1wherein the reducing agent is selected from the group consisting ofsalts of formic acid, salts of carboxylic acids other than formic acid,carboxylic acids, low molecular weight aldehydes, sugars, hypophosphite,borohydride, aminoboranes, lithium aluminum hydride, hydrazine, lowmolecular weight alcohols, and mixtures thereof.
 10. The method of claim9 wherein the reducing agent is selected from the group consisting offormaldehyde, sodium hypophosphite, sodium formate, gluconate, oxalate,sodium borohydride and mixtures thereof.
 11. The method of claim 1wherein the reducing agent is added to the plating slurry in an amountsufficient to reduce substantially all of the nickel and/or cobalt ionsin the slurry to the corresponding metal.
 12. The method of claim 1wherein the reducing agent is added to the plating slurry in astoichiometric amount sufficient to achieve the redox reaction with themetal ions in the slurry.
 13. The method of claim 1 further comprisingadding a chelating agent to the plating slurry.
 14. The method of claim1 further comprising adding a stabilizer to the plating slurry.
 15. Themethod of claim 14 wherein the stabilizer is a metal selected from thegroup consisting of chromium, titanium, niobium, tantalum, zirconium,vanadium, molybdenum, manganese, tungsten, bismuth, and mixturesthereof.
 16. The method claim 1 wherein the sponge support is maintainedunder a non-oxidizing atmosphere during steps (a)-(e) of the method. 17.The method of claim 1 wherein in step (d) the pH of the plating slurryis adjusted to a pH of at least about 5.5 and the temperature of theplating slurry is adjusted to at least 30° C.
 18. The method of claim 1further comprising initiating the deposition of nickel and/or cobalt onthe support by electrochemical displacement prior to step (d).
 19. Themethod of claim 18 wherein the deposition of nickel and/or cobalt isinitiated by adjusting the pH of the plating slurry to about 5 andmaintaining the pH for a time sufficient to initiate electrochemicaldisplacement of support metal by nickel and/or cobalt from the platingslurry.
 20. The method of claim 1 wherein steps (a)-(e) are repeated toapply multiple coatings of nickel and/or cobalt on the support.
 21. Themethod of claim 1 further comprising step (f), which is washing thecatalyst for a time and at a temperature sufficient to neutralize orremove substantially all residues and salts.
 22. The method of claim 1or 21 further comprising depositing a metal promoter on the surface ofthe catalyst.
 23. The method of claim 22 wherein the metal promoter is ametal selected from the group consisting of chromium, molybdenum,titanium, zinc, vanadium, zirconium and mixtures thereof.
 24. The methodof claim 23 wherein the metal promoter is in a zero valent state. 25.The method of claim 23 wherein the metal promoter is in an oxidizedform.
 26. The method of claim 21 further comprising depositing aprecious metal dopant on the surface of the catalyst.
 27. The method ofclaim 26 wherein the precious metal dopant is a metal or a compound of ametal selected from the group consisting platinum, palladium, iridium,rhodium, osmium, ruthenium, rhenium and mixtures thereof.
 28. A methodof preparing a nickel and/or cobalt coated sponge catalyst, whichcomprises (a) a metal sponge support having a surface and comprising (1)about 2 to about 40 weight percent of a metal selected from the groupconsisting of nickel, cobalt and mixture thereof, and (2) at least onemetal which is different from the metal(s) coated on the metal spongesupport, and (b) a metal selected from the group consisting of nickel,cobalt, and mixture thereof, coated on at least a portion of the surfaceof the metal sponge support, the method comprising: (a) preparing anaqueous slurry containing a metal sponge support having surface area,and comprising (1) about 2 to about 40 weight percent of a metalselected from the group consisting of nickel, cobalt and mixturethereof, and (2) at least one metal which is different from the metal(s)coated on the metal sponge support; (b) adding to the aqueous slurry asalt of a metal selected from the group consisting of nickel, cobalt andmixture thereof, in an amount sufficient to deposit a catalyticallyeffective amount of the metal on at least a portion of the surface areaof the metal sponge support and to form a plating slurry containing ionsof metal; (c) adding a reducing agent to the plating slurry in an amountsufficient to reduce the metal ions in the slurry to the correspondingmetal; (d) adjusting the pH and temperature of the plating slurry in amanner sufficient to deposit the metal on the surface of the support andform the nickel and/or cobalt coated metal sponge catalyst; and, (e)removing the nickel and/or cobalt coated metal sponge catalyst from theplating slurry.
 29. The method of claim 28 wherein in step (d) the pH ofthe plating slurry is adjusted to a pH of at least about 5.5 and thetemperature of the plating slurry is adjusted to at least 30° C.
 30. Themethod of claim 28 further comprising initiating the deposition ofnickel and/or cobalt on the support by electrochemical displacementprior to step (d).
 31. The method of claim 28 wherein steps (a)-(e) arerepeated to apply multiple coatings of nickel and/or cobalt on thesupport.
 32. The method of claim 28 further comprising step (f), whichis washing the catalyst for a time and at a temperature sufficient toneutralize or remove substantially all residues and salts.
 33. Themethod of claim 28 further comprising depositing a metal promoter on thesurface of the catalyst.
 34. The method of claim 32 further comprisingdepositing a metal promoter on the surface of the catalyst.
 35. Themethod of claim 28 further comprising depositing a precious metal dopanton the surface of the catalyst.